I am refurbishing an old sailboat, but I am confused regarding various shorepower options including converters vs. inverters vs. battery chargers. What type of shorepower system do you recommend for someone on a "beer budget?"
Tom Wood responds:
A converter and a battery charger are virtually the same—they convert 120-volt AC power to 12-volt DC. An inverter does the opposite, turning 12-volt battery power into useable 120-volt power when away from shorepower or a generator. Some models combine the two functions in one box. It sounds as if you want a battery charger and there are many models from which to choose, ranging from the simple, one-bank automatic to fancy multi-stage, multi-battery units in shiny stainless steel cases.
If you're truly on a beer budget, I'd recommend that you buy a portable automotive battery charger, an exterior grade extension cord, a circular twist-lock to three-prong electrical adapter, and then you'll be in business for under $100. Run the power cord in the companionway to the charger on nice days and charge your batteries while you drink the beer in the cockpit. This is, however, not a very elegant solution, and may appear rather socially incorrect at an upscale marina. Worse, the chargers are inefficient and many have to be tended, since they are not automatic.
For a real, permanent shore-power setup, you’ll need the following:
1. A shore-power cord, usually yellow, 50-feet long, and with the proper twist-lock end for your marina (most use 120-volt, 30-amp models).
2. An inlet into the boat, available in chromed metal or budget plastic.
3. Ten-gauge wire, preferably tinned, stranded three-conductor boat cable.
4. A master breaker panel,most come with power-on and reverse-polarity indicator lights.
5. A marine-grade battery charger of the proper number of amps and battery banks to suit your battery configuration.
The price for these five parts along with the miscellaneous terminal ends, wire ties, heat-shrink tubing, and fasteners should set you back about $500. If you bargain hunt in the SailNet Store, you may still be able to afford a six-pack. Plan to have at least a weekend to install the system, and be careful with 120-volt AC power because it can be lethal.
But since you’re going this far, you might as well upgrade the master-breaker-only panel to one with incoming power ammeter and voltmeter and three additional circuit breakers. You can then use the three circuits to add some GFI duplex outlets on the boat, one duplex each in the head and galley, and a few in the main salon would let you run the blender, coffeemaker, drill, TV, or any other household tool or appliance at the dock. Increasing the scope of the project to this point will add another $200 or so to the budget and a weekend to the work list, but it will also add real value to the boat.